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bad relay, bad plug? how can it work and not? #2699555
09/21/19 04:00 PM
09/21/19 04:00 PM
Joined: Feb 2003
Posts: 8,660
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Andrewh Offline OP
master
Andrewh  Offline OP
master
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Joined: Feb 2003
Posts: 8,660
so coronet running a 5.9 mag, using megasquirt.

Car up and died on me this morning. no reason.

I traced it back to the relay that powers the coil.

I literally replaced it 5 times with known good ones, and the one that powers the fuel pump and they all didn't work/acted wonky.

I built a bypass using a short piece of line and 2 spade connectors and it runs perfect.

I found a spare hella relay and tried it.
Car fired up but then started running rough and eventually died and would not restart.
I put the bypass back in and it fired up fine. no rough running or anything.

Do I just need to go buy a new relay? Is it the plug?
Ground? I can't see it working at all if any of these are "bad". It seems to be intermittent or after "working" for a while.

Re: bad relay, bad plug? how can it work and not? [Re: Andrewh] #2699557
09/21/19 04:06 PM
09/21/19 04:06 PM
Joined: Feb 2003
Posts: 1,637
Florida
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GMP440 Offline
top fuel
GMP440  Offline
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Posts: 1,637
Florida

Check the plug connectors that relay gets plugged into. Since you used diffferent relays there, I would check the connector terminals; if all good check wiring going to the relay connector plug.

Re: bad relay, bad plug? how can it work and not? [Re: GMP440] #2699604
09/21/19 07:12 PM
09/21/19 07:12 PM
Joined: Jan 2003
Posts: 15,197
Omaha Ne
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TJP Offline
I Live Here
TJP  Offline
I Live Here
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Joined: Jan 2003
Posts: 15,197
Omaha Ne
Originally Posted by GMP440

Check the plug connectors that relay gets plugged into. Since you used diffferent relays there, I would check the connector terminals; if all good check wiring going to the relay connector plug.


great suggestions as the different relays may have spread the terminals,

What type of relay??? Got a picture??
Is the relay sized properly for the load ?? A 30 amp draw should have a 45+ Amp relay IMO.
Some relays are rated for intermittent operation while others are continuous.
Take the cover off if possible and inspect the contacts twocents beer

Re: bad relay, bad plug? how can it work and not? [Re: TJP] #2699613
09/21/19 07:44 PM
09/21/19 07:44 PM
Joined: May 2019
Posts: 6,175
nowhere
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Sniper Offline
master
Sniper  Offline
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Joined: May 2019
Posts: 6,175
nowhere
There are two parts to a relay. Both parts need to work for you.

The first part is the contacts that connect your load to the power supply, your jumper is doing that part for you. This is the kiad sid eof the relay.

The second part is what controls the relay, it has a ground and 12V, this is the control side of the relay. You need both for the relay to function. I don't which of them is being switched by the MS system, usually it's the ground side. That is most likely where your problem lies. Probably a funky connection at either end or the wiring in between. When I wire relays I like to switch the ground side and I just tap into the load power supply for the 12V on the control side of the relay. I would look there.

Re: bad relay, bad plug? how can it work and not? [Re: Sniper] #2699638
09/21/19 09:22 PM
09/21/19 09:22 PM
Joined: Feb 2003
Posts: 8,660
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Andrewh Offline OP
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Andrewh  Offline OP
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Joined: Feb 2003
Posts: 8,660
I ordered some new ones.
it is the standard bosch type relay 5 pin type.
I don't think it is a heavy load, it is 12 volts to the pos side of the coil.
It is fused at 20 amps so it shouldn't pull more than that.

This is left over stuff I wired into from the original efi setup.
I am just going to rewire that section.

It is 2 relay's.
Both are grounded by the MS. full time power to 1 pin, and the side that switches it is powered by key on power.

I am going to rewire it so the ms only grounds 1 relay. power from that relay will trigger the other and the fuel pump relay. that way nothing is drawing off that ms relay at all. or I might eliminate the second relay all together. haven't decided yet. Will know when I Start pulling wiring out.







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